A typical conventional printing apparatus is an impact dot matrix type printing apparatus. As shown in FIG. 18, the impact dot matrix printing apparatus mainly comprises a print head 10, print wires 11, a carriage 12, a shaft 13, a fabric ribbon 14 and the like. The principle of printing is that when an electrical signal is applied to an actuator (not shown) in the print head 10, the print wire 11 connected to the actuator moves forward through a wire guide (not shown)to hit the fabric ribbon 14 and a recording paper 15, which causes ink in the fabric ribbon 14 to be transferred to the recording paper 15, thereby forming one pixel by each print wire. The print head 10, mounted on the carriage 12, can move smoothly on the shaft 13, the print wire 11 operates when the print head 10 comes at a predetermined position to form letters and the like. The actuator includes those of a plunger type, a pole type, a clapper type, a spring charge type, a moving coil type, a piezoelectric type, and the like. In general, actuators of the clapper type and the spring type are popularly used.
The recording paper 15 is of a type which a plurality of sheets are stacked and sense to a pressure to achieve copying. Normally, copying is possible by stacking a carbon paper called a pressure-sensitive paper or plural sheets of carbonless paper, and these are widely used for slips, receipts, and the like. Presently, the carbonless paper is predominantly used.
FIG. 19 shows a construction example of the recording paper 15 using the carbonless paper. In FIG. 19, the recording paper 15 comprises a top paper 16 positioned at the top, a bottom paper 18 positioned at the bottom, and necessary number of middle paper 17 positioned in the middle. The top paper 16 comprises a paper 19, which is a paper with a color former 20 coated on the back side, the middle paper 17 comprises a paper 19 with a color developer 21 coated on the surface and the color former 20 coated on the back side, and the bottom paper 18 comprises a paper 19 coated on the surface with the color developer 21. The color former 20 is an aggregate of microcapsules containing a dye, which opposes the color developer 21 and, when a load over a limit pressure is applied, the microcapsules at the portion are broken to release the dye, developing a predetermined color by a chemical reaction with the color developer 21. This is the principle of copying in the carbonless paper.
FIG. 20 shows a construction example of the recording paper 15 using carbon paper. One which is shown in FIG. 20(a) comprises a top paper 22, necessary sheets of a middle paper 23, and a bottom paper 24, the top paper 22 and the middle paper 23 are the same which are coated on the back side with a carbon layer 25 comprising a mixture of carbon and oil or wax. The bottom paper 24 is a paper and has no carbon layer. One which is shown in FIG. 20(b) comprises plural sheets of a paper 26 and a thin carbon paper 27 having the carbon layer 25 on the back side, which are inserted between the individual sheets. These recording paper 15 are the same as carbonless paper in that transfer is achieved by a pressure. Therefore, recording paper using the carbonless paper will be described below, which is also true for the carbon paper.
When two copies are required in addition to the original printed matter, the top paper 16, the middle paper 17, and the bottom paper 18 as shown in FIG. 19, for example, are stacked one sheet each in a predetermined order, and set on an impact dot matrix type printing apparatus so that they are pressurized by the print wire 11 from the upper side, thereby obtaining favorable copies. The number of copies achieved by the impact dot matrix type printing apparatus is normally 3 to 6 sheets. The number is 4 to 5 sheets for manuscript by a ball-point pen, and 6 to 10 sheets for an electric typewriter.
In addition to the impact dot matrix type, there are a thermal transfer type and an ink jet type, but any practical apparatus which enables copying is not yet available.
Therefore, with the recent increase in the information processing capacity by computers and needs for outputting large amounts of computer-processed information, slips and receipts requiring copying are going on increasing, however, copyable printing apparatus has been limited to that of impact dot matrix type.
However, the impact dot matrix type printing apparatus has a problem in that it generates high noise during printing which gives others an unpleasant feeling. That is, depending on the location of use, the printing apparatus is required to have a copying function and to be as low in noise as possible during printing, but the impact dot matrix type printing apparatus is not suitable for such applications.
To eliminate the above prior art problems, the primary object of the present invention is to provide a printing method and apparatus which has a copying function and is low in noise.